Process for producing inverted incandescent mantles.



0. K. HARDING.

PROCESS FOR PRODUCING INVERTED INOANDEBOBNT MANTLES.

APPLICATION 21111111 11111. 10, 1011.

992,959 1 Patented May 23, 1911.

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UNITED STATES PATENT OFFICE."

CHARLES KNOX HARDING, OF CHICAGO, ILLINOIS.

PROCESS FOR PRODUCING INVERTED INGANDESCENT MANTLES.

To all whom it may concern:

Be it known that I, CHARLES Knox HARD- ING, a citizen of the United States, and a resident of Woodlawn, city of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Processes for Producing Inverted Incandescent. Mantles, of which the following is a specification.

This invention relates, generally, to incandescent structures for lighting made by what has been generally known as the Welsbach process, which consists of impregnating a knitted fabric of cotton or other fibrous cellulose with solutions of the refractory earths, which are to constitute the finished mantle. The dimensions of this impregnated fabric are usually from 100 to 200% greater than that of the finished product after the cellulose and other vola= tile matter is burned out, but this large structure is fashioned and formed to such a shape as will produce the desired form and size of the finished mantle after it has been shrunken.

This process or method of construction takes advantage of the fact that the unequal shrinkage in the direction of the length and width of knitted fabrics enable a structure to be made therefrom of materially different shape from the shape that the finished mantle is to assume, and it is most desirable to shape the fabric mantle so that, on burning out, it will, most naturally and easily, assume the more symmetrical shape desirable in the finished resulting structure when the combustible matter has been burned out without being subjected to unequal stresses and strains which would injure the finished structure.

My invention relates particularly to an improved construction of inverted mantles, having an upper cylindrical body portion and a semi-spherical closed lower end portion, that possess advantages not attained by mantles manufactured prior to my invention, nor by the methods heretofore employed.

Among the objects of my invention is to facilitate the production of inverted mantles of uniform and symmetrical shape and facilitate their manufacture with the greatest economy of time, skill and labor without sac- Specification of Letters Patent.

Application filed January 10, 1911.

Patented May 23, 1911.

Serial No. 601,920.

rificing any of the prerequisites necessary where the best results are required.

In the acompanying drawings I have shown one embodiment of my invention which will illustrate a form of apparatus, and in what manner the process is to be performed, but many of the details shown may be modified without departing from the nature and scope of my invention which will be more explicitly pointed out in the claims.

I will describe my process as'applied to the manufacture of an incandescent structure similar to that shown in my U. S. Patent No. 982,958, dated January 31, 1911.

In the drawings Figure 1, is a vertical longitudinal section on line 11 Fig. 3 of the mold employed. Fig. 2, is a vertical cross-section on line 2-2 Fi 3. Fig. 3, is a top plan view of the mold. Fig. 4, is a bottom plan view showing the rectangular opening for holding the mold in proper posi tion. Fig. 5, is a side elevation of a section of tubular fabric of which the body portion of the mantle is formed. Fig. 6, is a side elevation of an elliptical shaped section of a single thickness of mantle fabric, cut lengthwise from knitted fabric, which forms a large part of the elon ated closed end portion of the mantle. elevation of the mold and shows a sewn and impregnated mantle on the mold in the position in which it is desiccated and formed to the desired shape. Fig. 8, is a side elevation of a burned-out finished mantle attached to a carrying ring, and the dotted line E indicates the position of the seam which unites the circumference of the bottom portion to the lower edge of the body portion.

Both upright and inverted incandescent mantles have generally been made from tubular knitted fabric, which has special properties which peculiarly fit it for the purpose. The typical mantle fabric is knitted on a circular machine having from eighty-eight to ninety-six needles in its circumference, each needle forming a chain of loops lengthwise of the fabric so that the fabric has about ninety-two loops around a circumference of about 5 inches, and each loop is composed of a pair of threads extending lengthwise of each loop, and has about 11 chains of loops to the inch of length of the fabric, so that a square inch of fabric has more than three times as many threads running lengthwise as. it has crosswise. This unequal distribution 'of the amount of threads materially facilitates the forming of cylindrical mantles, and gives them a preponderance of strength in an up and down direction, and in burning out the fabric the shrinkage is partly resisted by the force of gravity and partly by the pressure of the gas flame within the mantle, so that it results that the mantle having the greatest strength and least resistance shrinks much more in a vertical direction. than it does circumferentially.

I have discovered that a square section of knitted fabricbest adapted for upright mantles, and having the major portion of its threads running lengthwise of the fabric, when burned off and subjected to a uniform gas pressure, would produce a rectangular section in the resulting burned out structure having dimensions at least 50% greater along the lines of least resistance.

Most of the inverted mantles, in practical use, have been made from a section of tubular knitted fabric, the lower end being formed by gathering the lower edge of the tube and drawing it to the center. This resulted in a thickening or bunching of the goods at and around the center of the lower portion of the mantle, which was objectionable. To obviate this, especially for larger and heavier mantles made of coarser thread,

goring has been employed; that is, from two to six curved seams have been sewn through two adjacent layers of fabric from a point above the bottom where the diameter was to be retained to a point in the central axis at the bottom. These gores permit a quantity of stock to be cut out, but the seams, themselves, interfere with the incandescence at the central point, which is the most abundantly supplied with gas from its favorable location to the center of the flame. As a greater number of these gores are employed, the shape of the sewn fabric, as well as the shape of the resulting mantle after being burned off, becomes progressively more symmetrical, but the seams running to the center ofthe lower portion of the mantle are objectionable, and the more seams employed, the more objectionable they become, so that in many self-shaping mantles, commonly called fabric mantles, put on the market the symmetry is often sacrificed by decreasing the number of gores.

Prior to my invention, it was customary to cut and form the mantle fabric to closely approximate the shape of the finished burned out mantle, and to dispose the fabric, which was to form the closed end portion, symmetrically around the central axis at the end. According to my invention, I cut and sew the fabric without regard to securing a symmetrical hemispherical closed end where a knitted fabric is employed for the'fabric mantle, and secure additional advantages as well as perfect symmetry in the finished product. 7

IV here inverted mantles were made from a length of tubular fabric, the gores were cut out mostly, at a point adjacent to the center of the closed end of the mantle, the object being to reduce the quantity of goods in the circumference of the lower end of the tube so that the edges of the gores could be drawn together, and the curved sections between them, form a dome shaped, closed, lower end, these sections being formed the samesize, shape, length and width, and identically disposed in relation to the percentage of threads running lengthwise and crosswise of each section, it is obvious that, as eachsection has the number of threads disposed lengthwise, and that each one of all the sections extend the same length; from the lower end of the cylindrical body portion to the center of the round and lower end. The shrinkage will have a uniform effect on each of the sections, and if there are a large number of sections, the lower semicircumference of the unburned fabric mantle would be nearly equal, measured at an angle across the center of the dome shaped lower end while the finished mantle would also have a similar dome,

diametrically opposite sides of the mantle,

at the lower end of the cylindrical body portion; that is, in'the form shown the four corner pieces that would be cut out of a rectangular piece of fabric, the width and length of the ellipse shaped bottom C, two of which may be cut with a die from a section of tubular fabric, and the four corners cut out and not entering intothe construction of the mantle, which will serve the same purpose as in the prior method in whichfour gores were cut out and thrown away' at points surrounding the central axis in the bottom of the mantle. I cut and sew the portions that serve to form the closed end in the fabric mantle so as to form an elongated, rounded, terminal closed lower end portion having considerably longer horizontal dimensions in one direction than it has in the other at right angles thereto, but so arranged that the maximum shrinkage of the elliptical section,v or if the elliptical end is composed of more than one piece all the sections are combined to act in one direction; that is, the direction of the greatest length of the horizontally elongated bottom portion, and in the direction in which the major portion of the threads of the mantle fabric extend, and in the direction in which the shrinkage is normally or greater than it is in a direction at right angles thereto, and so arranged that the minimum shrinkage acts in the direction of the width of the elongated elliptical section at right angles to the longest dimension of the elongated lower closed end of the mantle, whereby a semispherical shape closed end portion is produced in the finished burned out mantle without having a symmetrical hemispherical body portion in the unburned fabric mantle with the attendant disadvantages of having all of the gores cut out from the points close to the center of the bottom portion of the mantle, and all of the seams radiating from the same point in the center of this most useful portion of an inverted incandescent mantle.

The length of an incandescent structure, produced from burning out impregnated knitted fabric, is.commonly about 50% of the length of such a structure before the combustible elements are removed, and two approximately circular sections of fabric, united together, would have a length sufficient to produce a burned out structure, whose length was approximately the diameter of one of said circles. In any case, however,the length of the long bottoms, which is to form the elongated closed end, of the knitted fabric mantle, will be very materially greater than the width of said elongated closed end portion.

In the art of knitting, a fabric is produced by forming a row of loops with a single thread, through which loops another row of loops are linked, and so on consecutively. The rows of loops crosswise of the fabric are properly referred to as rows of loops, and the series of loops endwise of the fabric are called chains of loops. In knitted mantle fabric the length of each loop is greater lengthwise of the fabric, and the width of each loop is less crosswise. As each loop has two sides and one end formed from a short piece of thread, and its lower end formed by the end of an adjacent loop, the shrinkage in the length of the thread in burning out, acts to reduce the length of the loops more than it does their width, and as there are many more loops to the inch of fabric measured crosswise than lengthwise, it results that the fabric has many more threads disposed lengthwise than it has crosswise of the fabric.

As heretofore mentioned, the superficial area of a given surface of impregnated mantle fabric, best suited for the manufacturing of incandescent mantles, would be about 150% larger than the superficial area of the desired structure remaining after the combustible and volatile mantle has been burned out, but it is clearly pointed out that the shrinkage is very materially different in the length and width of knitted fabric or in the direction in which the most or the least of the threads are disposed, especially if the most desirable form of knitted fabric is chosen to produce the strongest and most desirable finished incandescent mantle. The area of a section of impregnated mantle fabric would be represented by its length, multiplied by its width, and the area and shape of the structure resulting from burning out the same, would be represented and calculated by multiplying approximately 80% of its width by 50% of its length. The increased amount of shrinkage in the direction of its length of tubular knitted fabric does not interfere with the symmetry of the cylindrical body portions of inverted mantles, as this increased shrinkage takes place on all sides of a cylindrical body which are of equal length, but I have discovered that the best results from inverted mantles are produced by making the fabric portion, which is ultimately to form the bottom of a distinctly different shape; that is, extending much farther from the central axis in one direction and being much narrower in the other at right angles thereto, having widely different dimensions in length and width, by which means I have been able to produce a perfectly hemispherical symmetrical lower end portion of a finished mantle without producing stresses, strains and unequal stretching and distorting of its mineral filaments which constitute the finished mantle.

The nature of this invention is, therefore, an improved process of making an incandescent mantle adapted to produce an incandescent structure having a cylindrical open topped body portion and a hemispherical shaped closed lower end. Either before or after it has left the factory and been transported to the customer, constructed from a tubular body portion of knitted fabric and the horizontally, elongated or elliptical or ellipsoidal closed, lower end, formed from one or more sections of knitted fabric in such a way that the maximum shrinkage occurs along the major axis of the horizontally elongated, closed, lower end.

The mold shown in Figs. 1, 2, 3 and 4 per forms. a number of new functions which are essential and determine the character, perfection and many qualities of the product made by this process.

Many of the fundamental, chemical and physical principlesinvolved in the manucould be or were produced without it.

facture of incandescence-structures from cotton or other cellulose fabrics have been preserved as trade secrets, and the importance of certain operations is not generally known to the public, but in order to illustrate the advantage derived from the use of my improved mold I desire to state that much better results can be produced by its use t ltl eln e cellulose of the fabric used is commonly impregnated with a solution containing thorium, nitric acid and a volatile liquid, and the maximum quantity of solution should be applied to the thread. It might be supposed that a smaller quantity of a stronger or denser solution might serve the same purpose, but as a definite chemical action must be brought about between the thorium, acid and cellulose and a compound of the three formed after the volatile liquid is removed, the exact composition of this solution is of great importance as the compound thus assumes the colloidal form and structure of the cellulose fibers or cells of the cotton thread so that when the combustible matter of the compound is removed by burning, there results a similicrum of the integral fibers which were originally cotton, but a considerable shrinkage takes place in the length of the fibers.

The chemical afiinity of nitric acid is so strong for both thorium and cotton that some degree of success is commonly met with by those most unskilled in the art, but for the best results it is necessary to have a device for holding, supporting, carrying and retaining the proper disposition of the fibers and shape of the fabric while it is being subjected to the various operations from the state of simple cotton until it finally assumes the state of a dry solid compound of the refractory oXid and dry cellulose, with the liquidizable and volatile matter eliminated, before it reaches the stage where the combustible ,matter is oxidized, gasified and eliminated, and the refractory elements of the structure undergo a shrinkage, largely in the direction of the length of the fiber, threads, loops and the lengths of the knitted fabric, and the lengths of the elongated closed end of the mantle, so that the threads may be disposed as far as possible in straight lines and'be able to undergo the shrinkage without bending or changing the shape of the curves, or producing movement of the threads at their point of contact with other threads and causing the lineal shrinkage to take place in the freely suspended portion between such points of contact.

The circumference of the elliptical shaped section C may be attached to thelower edge of the tubular body portion 13 by a seam E, produced in any suitable manner, but this operation can be conveniently performed by stretching the body portion over a mandrel having an: elliptical cross section and a flat end, and clamping the section C so its circumferential edge will project in the same 7;

plane as the lower edge of the body portion, and revolving the mandrel and the mantle thereon so as to pass the edges successively under the needle and feed of a suitable sewing machine.

Having now described my invention and illustrated one method by which it may be carried out, what I claim is:

1. The process of producing inverted incan-.

descent mantles from knitted fabric, which consists of cutting and sewing sections of said knitted fabric so as to form a tubular body portion and a horizontally elongated closed lower end, impregnating said fabric with solutions of refractory incandescible elements in. vaporizable solvents, forming the impregnated fabric over the surface of a mold, having a body portion of elliptical cross sec-v tion and a substantially semi ellipsoidal shaped end surface, with the major portion incandescent mantles from knitted fabric,

which consists in forming a fabric having a tubular body portion and an elongated elliptical shaped closed lower end of a single thickness of said knitted mantle fabric, applying impregnating solutions of refractory earths to said fabric, forming the impregnated mantle over the surface of a mold having a substantially semiellipsoidal shaped end surface, with the major portion of the threads of the fabric disposed lengthwise of the end of said mold, and subsequently burn ing out the combustible matter from said impregnated fabric mantle, whereby the increased shrinkage in the direction of the elongated closed lower end of said mantle fabric results in an approximately hemispherical shaped end, symmetrically disposed about the central vertical axis of the finished mantle.

3. The process of producing an inverted incandescent mantle having a cylindrical open topped body portion and a symmetrical hemispherical shaped closed lower end,

which consists of forming a mantle of impregnated knitted fabric. having a tubular body portion, and a horizontally elongated closed lower end portion of knitted fabric, having amajor portion of its threads disposed lengthwise of said elongated lower end surface, and unsymmetrioally disposed about In Witness whereof, I have hereunto set the central axis of the structure, and subsemy hand this 7th day of January, 1911, in quently burning out the combustible matter the presence of two Witnesses. of such impregnated fabric mantle and CHARLES KNOX HARDING.

5 shrinking the elongated closed end into the Witnesses:

form of a concentric hemispherical shaped ROBERT H. WEIR,

closed lower end. ARTHUR W. CARLSQN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. 0. 

